Pilot lamp station line circuits



WIME

Fm, 195i IT. V. WELQH PILOT LAMP STATION LINE CIRCUITS Filed June 9 1.949

.FL )ww Wm/ww I TL MWQUL@ @@WMW @@Hm@ www@ a I I @Q P @L SML@ .LIL mmm @TMA ,lumrm Hmmrmm SIMM mm L @MII @L @i 3mm, ML WWE L., .--LM www, L LME 3 ing of one switchboard panel in accordance with a modification of the invention.

Fig. 3 illustrates a further modication of the wiring of the pilot control relay.

Referring to Fig. 1, the four subscribers lines illustrated are designated lines I, 2, 99 and |00. Line I is shown terminating in multiple jacks I0, I I, I2 and I3 which occupy positions in panels Nos. 1, 8, 15 and 22, respectively, of the four switchboard multiples indicated. Line 2 is shown terminating in multiple jacks 20, 2|, 22 and 23 which also occupy positions in panels Nos. I, 8, I5 and 22, respectively, of the four switchboard multiples. Similarly, lines 99 and |00 are terminated in jacks 90, 9|, 92 and 93 and in jacks ||0, |I, |02 and |03, respectively, of the switchboard. Associated with each line jack is a lamp jack all of which but those associated with jacks II, 22 and |03 are shown housing a line lamp. All the lamp jacks located in panel No. I are individually serially associated with the winding of pilot control relay I4; all those located in panel No. 8 are similarly associated with the winding of pilot control relay 24; all those in panel No. I5 are similarly connected in series with the winding of pilot control relay 34, and those in panel No. 22 with the winding of pilot control relay 44.

Pilot control relays I4, 24, 34 and 44 control operating circuits for panel pilot lamps I5, 25, 35 and 45 respectively.

Each of the lines I, 2, 99 and |00 is shown terminating in the windings of a line relay I6, 26, 36 or 46, it being understood that actually the line conductors are connected to the line relay windings by way of armature contacts controlled by a cut-oil relay not shown, but well known in the art.

When a call is originated on any line, line I for example, the corresponding line relay I'B operates in well-known manner over the closed station loop. At its armatures and front contacts line relay I6 completes obvious operating circuits for the multiple line lamps I1, I8 and I9 which include the windings of pilot control relays I4,

v v34 and 44, respectively. The lamps I1, I8 and |9 j are lighted in these circuits and the relays I4, 34 -i' and 44 operate to complete obvious energizing circuits for panel pilot lamps I5, 35 and 45, re-

fspectively. The lighting of lamps I1, I8 and |9 identify, at their respective switchboard multiples, the calling line and the lighting of lamps I5, 35

and 45 serves to advise the attending operators that in each of panels Nos. I, I and 22 there is a line lamp lighted and a call on the corresponding line awaiting attention. Any operator having access to line jacks I0, I2 or I3 may answer the call in well-known manner. Answering the call at the switchboard results in the operation of the corresponding cut-off'relay (not shown) which, in turn and in well-known manner causes the deenergization of line relay I6. The line lamps I1, I8 and I9 are thus extinguished and, unless another call on any of the other lines is awaiting attention, relays I4, 34 and 44 release and extinguish their associated panel pilot lamps.

For explanatory purposes let it be assumed that the grounded back contact of each of the line relays I6, 28, 36 and 46 has been omitted and that prior to the origination of the call on line I, as

Idescribed, a call on line 2 had been originated.

This second call would have resulted in the'lighting of line lamps 21, 28 and 29 and also in the energization and operation of pilot control relays I4, 24 and'44 in a manner now apparent. If this second call is answered before the call on line I is answered it is obvious that line lamps 21, 28 and 29 would be extinguished and that pilot control relay 24 should be deenergized, since this relay does not operate on a call from line I because of the vacant lamp jack 3| in panel No. 8 to which the pilot control relay 24 is individual.

However, spurious current paths which include the winding of pilot control relay 24 may be traced back to battery at the armature contacts of the now operated line relay I6. One such path extends from grounded battery, over the armatures and front contacts of relay I6, filament of line lamp I1, filaments of line lamps 21 and 28 to ground by way of the winding of relay 24. Numerous other similar paths may be traced by way of the filaments of other line lamps. The current which traverses these paths is not great enough to light the lamps included therein but is of suilcient magnitude to maintain relay 24 operated, it being understood that the resistance of the line lamps is high in comparison to that of the windings of the pilot control relays.

Relay 24 therefore would remain operated under the assumed conditions when it should be released. Panel pilot lamp 25 therefore would be lighted falsely. To preclude such false operation of the pilot control relays each lamp lead controlled by a line relay is normally grounded by way of a back contact of the line relay. Hence the spurious current paths instead of finding ground potential by way of the winding of a pilot control relay, such as relay 24, nd direct ground at the right armature and back contact of the unoperated line relays. In this manner the spurious currents are diverted from the pilot control relays and their false operation precluded.

The wiring arrangement just described permits trafic loads at the switchboard to be varied at Will by the chief operator. For example, should it be found desirable to relieve the operator having access only to multiple No. I by decreasing the number of lines to be attended to by that operator, it is only necessary that one or more line lamps such as line lamp 49 be removed from its socket or jack and inserted elsewhere, ,if necessary, in the lamp jack 48, for example, located in multiple No. 4. Under this condition calls originated on line |00 would no longer appear at the switchboard section designated multiple No. I. This simple method of shifting of the load at the switchboard from multiple to multiple is made possible by the invention herein described. Heretofore any attempts to employ panel pilot lamps in a multiple switchboard resulted in false operation of the pilot control relays or involved wiring complexities which precluded the possibility of load shifts being made by the simple expedient of shifting line lamps on the board and necessitated the services of a maintenance man.

The line relays are illustrated with two armatures While it might appear that but one would suiilce. However, it is apparent that should battery be connected to the front contact controlled by the right armature of the relay, fuse blowing would result should a maintenance man apply an adjusting tool to the relay spring, the associated back contact of which is grounded and the corresponding front contact of which is connected to battery.

'I'he switchboard panel disclosed in Fig. 2 corresponds to panel No. I of Fig. 1 and, where possible, the same designations are used in the two figures to identify similar elements. They wiring of Fig. 2 :distinguishes from `thatof Fig. 11

principally cin the useof .individualfleads lfrom the line lamps .and of a .Well-known type of fuse structure :having `its `fusible `element included in series with the windingrof the -pilotcontrol relay.

The several individual 'lamp leads are designated by the numerals 5I, .52, 53 and 54 respectively. All of these leads are conductively connected to a common connector comprising the alarm stud 5510i the vfuse A. Aseparate lead 56 .also conductively `associated with the ralarm stud 55 extends therefrom to one terminal of the windings of relay Iii, the other terminal of which is connected to -the yfuse mounting Vstud 5'! by the conductor 58. The stud :51 is connected to a third grounded `fuse terminal 5.9 by way of a :fusible element 6 6 and a spring'fel. The :fuse A may be ci the .type disclosed :in Patent No.

817,959 to E. B. Craft, issued April 17, 1906.

When any of the line relays corresponding to the line lamps illustrated operate, the line lamps are lighted in circuits which include the winding of relay I4, fusible element 60, spring 6I and the grounded fuse mounting stud 59. Relay I5 operates and causes its associated panel pilot lamp I5 to be lighted.

In the event of an overload which may occur in times of panic caused by re or other abnormal occurrence it is possible that the current traversing the windings of relay I4 lmight exceed tolerable limits and cause an interruption or telephone service if ordinary fusing was depended upon. In the illustrated arrangement the excessive current causes the rupture of the fusible element 56 whereupon the spring element 6I moves into engagement with the fuse mounting stud 55 to extend the lamp leads 5I, 52, 53 and 54 to the grounded stud 59. Thus the line lamp circuits are maintained operative though the panel pilot lamp and its control relay are disabled. Telephone service therefore, is maintained uninterrupted under conditions when service continuity is most essential.

In Fig. 3 the lamp leads are connected to a common terminal 52 and a variable resistance, in the nature of a copper oxide varistor is connected in shunt with the winding of the pilot control relay I4. This arrangement serves also to prevent overheating.

What is claimed is:

l. In combination, telephone subscribers lines, a telephone switchboard comprising a line lamp for each of said lines, a pilot lamp, a relay for controlling the operation of said pilot lamp having one winding terminal connected to ground potential, means vconnecting one terminal of each of said line lamps to the ungrounded winding terminal of said relay, a line relay for each of said subscribers lines, operable means for normally maintaining the other terminal of the corresponding line lamp at ground potential and, when operated, for completing an operating circuit for its corresponding line lamp and said pilot control relay and means whereby said operable means are controlled by each of said line relays.

2. In combination, telephone subscribers lines, a telephone switchboard comprising a plurality of multiple sections, a line lamp for each of said lines in each of said sections, a pilot lamp individual to each section, a control relay for each pilot lamp having one winding terminal connected to ground potential, means connecting one terminal of each of the line lamps in any one section to the ungrounded winding terminal of the corresponding pilot control relay, a line relay foreach of said subscribers lines, -operableimeans for normally maintaining the other lterminal of each of the corresponding line lamps at ground Vpotential and, when operated, for completing operating circuits for the corresponding ,Eline lamps and their corresponding pilot control relays and means whereby said operable means are controlled by each of said line relays. f

.3. In combination, artelephone subscribers line. a line lamp for said line, a pilot lamp, a .control relay for said pilot lamp having one winding terminal connected to groundpotentiaLmeans connecting the other winding terminal of saidfcontrol relay to one terminal of said line lamp, a battery. a line relay for said line, means for normally connecting ground potential to the other terminal of said line lamp and, at other times, `for` ,connesting said battery thereto and Vmeans whereby said last means is controlled by said line relay.

4. In combination, a telephone subscribers line, a switchboard comprising a plurality of multiples, a line lamp for said subscribers line in each switchboard multiple, a pilot lamp for each multiple, a control relay for each pilot lamp having one of its winding terminals connected to ground potential, means connecting one terminal of each of said line lamps to the ungrounded winding terminal of the corresponding pilot control relay, a lamp lead common to the other terminal of each of said line lamps, and a line relay for said subscribers line normally connecting said common lamp lead to ground potential.

5. In combination, telephone subscribers lines, a switchboard, a line lamp for each of said lines at said switchboard, a pilot lamp common to said line lamps, a control relay for said pilot lamp, means including a fusible element connecting one of the winding terminals of said control relay to ground potential, a common connector, circuit means connecting the other winding terminal of said control relay to said common connector, individual circuit means connecting one terminal of each of said line lamps to said common connector, means for completing operating circuits for said line lamps and for the winding of said control relay, means whereby said last means is controlled over said subscribers lines, and means responsive to a rupture of said fusible element for connecting said common connector to ground potential.

6. In combination, telephone subscribers lines, a telephone switchboard of the multiple type, each multiple thereof including a plurality of vertical panels and each panel having a jack termination for each of said subscribers lines, a lamp jack for each of said jack terminations, said lamp jacks having means adapted to accommodate line lamps corresponding to said subscribers lines, at least one of said lamp jacks being vacant in certain of said vertical panels, a pilot lamp for each of said Vertical panels, a relay for controlling the operation of each of said pilot lamps having one winding terminal connected to ground potential, means connecting one terminal of each of the line lamps in a vertical panel to the ungrounded winding terminal of the corresponding pilot relay, a line relay for each of said subscribers lines, operable means which, when in normal condition, maintains the other terminal of each of the corresponding line lamps at ground potential and, when operated, completes operating circuits for the corresponding line lamps and their corresponding pilot control and means whereby said operable means is controlled by each of said line relays.

7 7. n combination with 'a telephone switchboard in which each ofv a plurality of subscribers lines is provided With a plurality of multiple jack terminations each located in a different one of a plurality of vertical panels and in Which each jack termination is provided with a lamp-accommodating jack and each vertical panel is provided with a pilot lamp and a corresponding pilot relay having a permanently grounded Winding terminal and in which at least one of the lampaccommodating jacks in at least one of the vertical panels is vacant, a line relay for each of said subscribers lines having a normal position and an operated position, means connecting the ungrounded terminal of each of said pilot relays A,

to one terminal of each of the lamp-accommodating jacks in the corresponding panel, means for connecting the other terminals of all its corresponding lamp-accommodating jacks to ground 8 potential, means whereby said last means is con'- trolled by each of said line relays when in normal position and means controlled by each of said line relays, When operated, for disconnecting ground potential from the said other terminals of its corresponding lamp-accommodating jacks and substituting battery therefor.

PAUL V. WELCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 810,367 Beyland Jan. 16, 1906 1,353,065 Paca Sept. 14, 1920 2,329,004 Shope Sept. '7, 1943 

